Add the red peppers, onion and pak choi into a deep frying pan/sauce pan on a high heat with the rapeseed oil. Fry for around 5 minutes and season with salt and chilli flakes.
Meanwhile, add the noodles to salted boiling water for around 3 minutes. Drain and add to a large bowl, tossing the noodles with the chilli oil and minced garlic.
Once the veggies have softened but still have a bit of crunch, stir the noodles into the pan and reduce the heat. Add the sweet soy sauce and soy sauce and toss until evenly coated. Season with salt and pepper.
Serve the noodles and garnish with spring onion and additional chilli flakes if you like it extra hot!